The diagnosis and treatment of patients with cancerous tumors, pre-malignant conditions, and other disorders has long been an area of intense investigation. Non-invasive methods for examining tissue include palpation, thermography, PET, SPECT, Nuclear imaging, X-ray, MRI, CT, and ultrasound imaging. When the physician suspects that tissue may contain cancerous cells, a biopsy may be done either in an open procedure or in a percutaneous procedure. For an open procedure, a scalpel is used by the surgeon to create a large incision in the tissue in order to provide direct viewing and access to the tissue mass of interest. Removal of the entire mass (excisional biopsy) or a part of the mass (incisional biopsy) is done. For a percutaneous biopsy, a needle-like instrument is used through a very small incision to access the tissue mass of interest and to obtain a tissue sample for later examination and analysis.
The advantages of the percutaneous method as compared to the open method are significant: less recovery time for the patient, less pain, less surgical time, lower cost, less risk of injury to adjacent bodily tissues such as nerves, and less disfigurement of the patient's anatomy. Use of the percutaneous method in combination with artificial imaging devices such as X-ray and ultrasound has resulted in highly reliable diagnoses and treatments.
Generally there are two ways to percutaneously obtain a portion of tissue from within the body, by aspiration or by core sampling. Aspiration of the tissue through a fine needle requires the tissue to be fragmented into small enough pieces to be withdrawn in a fluid medium. The method is less intrusive than other known sampling techniques, but one can only examine cells in the liquid (cytology) and not the cells and the structure (pathology). In core sampling, a core or fragment of tissue is obtained for histologic examination, genetic tests, which may be done via a frozen or paraffin section. The type of biopsy used depends mainly on various factors present in the patient, and no single procedure is ideal for all cases. However, core biopsies seem to be more widely used by physicians.
The following patent documents are incorporated herein by reference for the purpose of illustrating biopsy devices and methods: U.S. Pat. No. 5,526,822 issued Jun. 18, 1996; U.S. Pat. No. 5,895,401 issued Apr. 20, 1999; U.S. Pat. No. 6,086,544 issued Jul. 11, 2000; U.S. Pat. No. 6,620,111 issued Sep. 16, 2003; U.S. Pat. No. 6,626,849 issued Sep. 30, 2003; U.S. Pat. No. 6,638,235 issued Oct. 28, 2003; U.S. Patent Application 2003/0109803 published Jun. 12, 2003; U.S. Patent Application 2003/0199753 published Oct. 23, 2003; U.S. Patent Application 2003/0199754 published Oct. 23, 2003; U.S. Patent Application 2003/0199785 published Oct. 23, 2003; and U.S. Ser. No. 08/825,899 filed on Apr. 2, 1997.
In making and using biopsy devices for use with magnetic resonance imaging (MRI) machines, it is desirable to avoid distortion of the image provided by the MRI machine, yet still be able to accurately position the needle with respect to a desired location in a tissue mass.